Efficacy of gaseous chlorine dioxide in reducing Salmonella enterica, E. coli O157:H7, and Listeria monocytogenes on strawberries and blueberries

Abstract

Gaseous chlorine dioxide, a strong oxidizing agent can be utilized as an effective alternative sanitizing agent. This study evaluated the efficacy of low concentration (≤5 mg/L) gaseous chlorine dioxide (ClO₂) treatment with gas permeable sachets in reducing the levels of Salmonella, E. coli O157:H7, and Listeria monocytogenes on strawberries and blueberries. Strawberries and blueberries were spot inoculated (107 CFU/g) with multi-strain cocktails of each pathogen and dried for 120 min inside a biosafety cabinet. A treatment chamber was successfully designed to sanitize inoculated samples in sealed 5 gallon chambers containing gaseous ClO₂ sachets. The gaseous ClO₂ overhead concentration was maintained within the range of 3.32 ± 1.73 to 4.95 ± 2.19 mg/L for up to 3 h of treatment. Gaseous ClO₂ treatments reduced pathogen levels significantly (P < 0.05) on strawberry and blueberry samples. The reduction of E. coli O157:H7, L. monocytogenes, and S. enterica levels on strawberries were by 2.0 ± 0.83, 3.5 ± 0.18, and 2.9 ± 0.20 log CFU/g, respectively after 3 h of treatment while 3 hof gaseous ClO₂ treatment on blueberries reduced E. coli O157:H7, L. monocytogenes, and S. enterica levels by 2.3, 2.1 ± 0.28, and 2.2 ± 0.63 log CFU/g, respectively. The reduction of pathogen levels with treatment time was variable based on pathogen type. This study indicates that gaseous ClO₂ delivered in gas permeable sachets at low concentrations (≤5 mg/L) can significantly reduce pathogens on strawberries and blueberries during post-harvest sanitation.